A recent important application of fluorescent lighting has been the use in retail establishments, and the like, of strip lighting, particularly those having a high truss roof and rows upon rows of shelving approximately six foot in height. In the past, it has been customary that ceiling suspended banks of fluorescent lighting have fairly well saturated the interior of the retail establishment from a distance well above the shelves.
With the advent of increased consumer awareness as to the labeling and content of the packages, particularly food packages, the ceiling suspended lighting, even though it involves a large number of fixtures, often fails to provide adequate illumination for the purchaser at chest height to read fine print on labels. As a result a relatively new type of lighting in the form of continuous tubular fixtures which is located at approximately the seven foot height above the floor and extending along the length of the shelves providing strip lighting has found broad acceptance.
The tubular cross section fixture allows a single or double strip fluorescent lighting fixture assembly to be enclosed within the tubular enclosure with a window and lens directed downward and in certain cases angled inwardly toward the shelf. Typically, the enclosures are six inches in diameter with approximately 120 degrees of a circle in the form of a curved linear fresnel lens to provide the desired lighting pattern.
Typically, tubular fixtures of this type have the fluorescent lamp and electrical lamp components integrated into the enclosure and the assemblies come in preassembled lengths usually slightly more than 8 feet in length to enclose a standard 8 foot fluorescent lamp assembly. The enclosure itself is usually extruded aluminum in the form of generally 240 degrees of circular cross section with internal bosses designed to provide support points for 120 degrees of lens and additional support points for the fluorescent lamp assembly. Examples of lighting fixtures of the type discussed above may be found in the following U.S. Patents:
______________________________________ 4,390,930 Douglas J. Herst June 28, 1983 4,420,798 Douglas J. Herst December 13, 1983 4,274,657 Douglas J. Herst July 10, 1984 4,573,111 Douglas J. Herst February 25, 1986 ______________________________________